EMPLOYEE WAS CLIMBING THE LADDER INTO HER OFF ROAD DUMP TRUCK #884 WHEN HER FOOT SLIPPED, SHE FELL TO THE GROUND INJURING HER KNEE. WEATHER CONDITIONS WERE COLD AND WET. CAUSATION: MUST USE EX TRA CAUTION AND MAINTAIN THREE POINTS OF CONTACT WHEN MOUNTING AND DISMOUNTING EQUIPMENT IN WET WEATHER CONDITIONS.